1. Field of the Invention
The present invention relates to apparatus for detecting a rotational state of a wheel mounted on a vehicle.
2. Related Background Art
Japanese Patent Application Laid-Open No. 2000-187039 discloses a system including a pair of sensors per rotating body, e.g., a wheel, and adapted to detect a rotational direction of this rotating body in accordance with phase states of detection outputs from the pair of sensors.
In use of the rotational state detecting system as described above, however, when a wheel is in a halt (including states equivalent to a halt), the system can sometimes fall into such an unstable state that the output of rotational direction of the wheel is indistinguishable or the system can sometimes output an incorrect rotational direction because of influence of an external magnetic field, a magnetic environment, or the like. Such output signals are unwelcome to optimal operations of on-vehicle systems including an antilock brake system (hereinafter referred to as ABS) and others in certain cases.
An object of the present invention is, therefore, to provide rotational-state-of-wheel detecting apparatus that can avoid the output of the incorrect rotational direction and the unwanted change of rotational direction even during halts of a vehicle.
In order to accomplish the above object, a rotational-state-of-wheel detecting apparatus according to the present invention is an apparatus for detecting a rotational state of a wheel, comprising a rotating member which rotates together with the wheel, a detected portion provided at the rotating member, detecting means for detecting passage of the detected portion to output a detection signal, and rotational direction detecting means for detecting a rotational direction of the wheel, based on the output of the detecting means, the apparatus further comprising halt detecting means for detecting whether the wheel is in a halt or not, and restricting means for restricting a change of the rotational direction detected by the rotational direction detecting means, when the halt detecting means detects that the wheel is in a halt.
In the above rotational state detecting apparatus, when the halt detecting means detects that the wheel is in a halt, the restricting means restricts the change of the rotational direction detected by the rotational direction detecting means, so that the apparatus can avoid repetitive switching of output between forward and backward rotational directions and output of an incorrect rotational direction in a state in which the wheel is judged in a halt.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.